There
I was in a Fort Lauderdale hotel lobby, learning about thermal imaging
by watching women and seeing a lot. "X-ray glasses, an adolescent
boy's dream!" I thought, and wondered if the lads at D&B
Technology intended a double meaning when they branded their new line
of infrared viewing devices HotEye.

But
after further testing at the end of a dark dock, and a long conversation
with D&B president Bob Gravely, I'm convinced that HotEye is
an innocent product and, though expensive, possibly a real lifesaver.
To appreciate the potential of thermal imaging, and particularly to differentiate
it from more common night vision tools, you need some background on the
technologies.

Visible
light is electromagnetic radiation within a certain frequency band, and
most everything we see--fires and the like excepted--is reflecting
light from another source. That's because a thing has to be darn
hot to radiate visible energy. However, every object, even an ice cube,
radiates infrared energy--that is, energy below ("infra")
the lowest visible frequency (red)--in proportion to its temperature.
Back in the 1960s some serious defense industry R&D went into developing
an electronic way to distinguish small differences in infrared (IR) radiation
and convert them into a visible video signal, ultimately a target.

Meanwhile,
other engineers with similar goals developed "light amplifying"
electronics that can multiply glimmers of reflected star- or moonlight
thousands of times. A high-end modern unit, like ITT's Night Mariner
160, claims a 50,000 amplification factor, able to detect a man at a distance
of 1,800 feet in starlight, farther with optional magnification. It has
the form of a monocular and retails at around $1,800. (Some night-vision
units come with "infrared illuminators" for short-range work
in pitch black; they are using "near" IR, which is reflective
and of slightly different frequency than thermal IR.)

At any
rate, the big plus for mariners with either type of night-vision instrument
is the ability to see dangers like floating logs and nonmetallic vessels
that radar might easily miss. Both light-amplifying and thermal viewers
produce monochromatic, slightly fuzzy images, but the similarity is superficial.
For instance, with either tool you can make out a person walking down
a pier in near total darkness; but with the thermal imager you might also
see his slightly warm footprints trailing behind him. Similarly, harking
back to my demo in the hotel lobby, a thermal detector can magically map
the way a person's body heat transmits through his or her clothing
(note to privacy lawyers: You're not really peering through the
clothing, it just looks that way).

So seeing
heat is truly different and presents some interesting, even practical,
possibilities. If you look around your engine room with something like
the HotEye 3x, you might very well see tiny oil or exhaust leaks. If you
inspect your hull when the engines are warmed up, you should be able to
make out structural elements, perhaps even a bad weld or a cracked frame.
This sort of special sight works particularly well on the thermally flat
plane of the ocean. The relatively hot head of a man overboard will show
up like bright light.